The field of the invention is radio frequency (RF) signal transmission, transmission lines and balanced to unbalanced impedance transformation and simultaneously to split a single balanced input RF signal into a first and second quadrature unbalanced RF output signals. Similarly, the combination of a first and second unbalanced quadrature RF input signals may be combined into a single RF output signal. It will be appreciated, however, that the invention is also amenable to other like applications.
Magnetic resonance imaging (MRI) tomography is a known technique for acquiring images of the inside of the body of a living examination subject. To this end, magnetic gradient fields and an RF field, which are generated by gradient and RF coils respectively, are superimposed on a static magnetic field. The gradient fields that influence the examination subject are characterized by a magnetic flux density that varies over time, which may be utilized for imaging techniques. In certain MR systems, birdcage RF coils are employed, which require quadrature excitation and reception. Such quadrature excitation and reception is commonly achieved with a 90 (ninety) degree splitter-combiner. Additionally, to reduce system noise and cable currents, a balanced to unbalanced (balun) transformer is commonly employed.
It is well known in the art that a typical RF power transmission requires some form of RF power amplifier and transmission line. The interfacing of RF componentry usually requires the amplification, combination, and splitting of RF signals. The combination is usually performed by a splitter-combiner, which may further require the use of a balun or transformer. The balun performs a balanced-to-unbalanced (balun) transformation.
Commonly in the art, a power amplifier circuit must be cascaded with balun impedance transformers to match the impedance of the amplifier. Thus, the prior art requires a power amplifier cascaded with the balun impedance transformers to enable RF power to be split, amplified and then recombined at a higher power level.
Utilizing separate components for each function adds size cost and weight to existing MRI systems. What is needed in the art is a quadrature splitter-combiner integrated with a balun transformer.
The above discussed and other drawbacks and deficiencies are overcome or alleviated by an integrated quadrature splitter-combiner and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and said balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, the third capacitor, and the transmission line balun combine to form an RF splitter-combiner to split a balanced RF signal received at the first port into a first and second unbalanced quadrature RF signal transmitted at the second port and combines the first and second unbalanced quadrature RF signals received at the second port into the balanced RF signal transmitted at the first port.
Also disclosed herein an exemplary embodiment is an integrated quadrature splitter and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and the balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, the third capacitor, and the transmission line balun combine to form an RF splitter to split an balanced RF signal received at the first port into a first and second unbalanced quadrature RF signals transmitted at the second port.
Further, disclosed herein another exemplary embodiment is an integrated quadrature combiner and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and the balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, the third capacitor, and the transmission line balun combine to form an RF combiner to combine an unbalanced quadrature RF signal received at the second port into a balanced RF signal transmitted at the first port.
Disclosed herein in yet another exemplary embodiment is an imaging system comprising: a imaging system with quadrature RF coils; an integrated quadrature splitter or combiner and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and said balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, the third capacitor, and the transmission line balun combine to form an RF splitter or combiner to either split a balanced RF signal received at the first port into a first and second unbalanced quadrature RF signals transmitted at the second port or to combine the first and second unbalanced quadrature, RF signals received at the second port into the balanced RF signal transmitted at the first port.
Also disclosed herein is a magnetic resonance imaging system comprising: a magnetic resonance imaging system with quadrature RF coils; an integrated quadrature splitter-combiner and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and the balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, the third capacitor, and the transmission line balun combine to form an RF splitter or combiner to either split a balanced RF signal received at the first port into a first and second unbalanced quadrature RF signals transmitted at the second port and to combine the first and second unbalanced quadrature RF signals received at the second port into the balanced RF signal transmitted at the first port.
In another exemplary embodiment, disclosed herein is a method of splitting a balanced RF signal into unbalanced quadrature RF signals comprising: receiving a balanced RF signal at first port of an integrated quadrature splitter and balun, the integrated quadrature splitter and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and the balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, said third capacitor, and said transmission line balun combine to form an RF splitter. The method also includes generating a first and second unbalanced quadrature RF signals transmitted at the second port.
In yet another exemplary embodiment, there is disclosed herein a method of combining unbalanced quadrature RF signals into a balanced RF signal comprising: receiving a first and a second unbalanced quadrature RF signals at second port of an integrated quadrature combiner and balun, the integrated quadrature combiner and balun comprising: a transmission line balun operably connected to a first port and a second port; a first capacitor operably connected across the transmission line balun; a second capacitor operably connected to the first port and the balun; and a third capacitor operably connected to the second port and the balun. The second capacitor, the third capacitor, and the transmission line balun combine to form an RF combiner. The method also includes generating a balanced RF signal transmitted at the first port.